Robot hand

TECHNICAL FIELD

This invention relates to a robot hand, particularly to the structure of the fingers of a robot hand.

BACKGROUND ART

The fingers (more specifically, finger tips) of a robot hand are generally formed of a single material having an appropriate coefficient of friction (e.g., silicone rubber). In contrast, the below-mentioned Non-patent Ref. No. 1 teaches formation of a finger tip from a skeletal frame and a nail made of aluminum, and skin made of soft sponge that covers the skeletal frame. Further, as set out in Patent Ref. No. 1, rigid inner skin is provided to cover a tactile sensor attached to a base portion serving as a skeletal frame and flexible outer skin is provided to cover the inner skin.

Non-patent Ref. No. 1: Paper at the 16th Annual Conference of the Robotics Society of Japan, “Development of finger-tip of its structural design aimed at adjustment of contact area,” Robotic Society of Japan, September 1998, pp 1437-1438.

Patent Ref. No. 1: Japanese Patent Publication Hei 7(1995)-8477

DISCLOSURE OF INVENTION

Problems to be Solved by the Invention

The fingers of a robot hand should preferably be high in coefficient of friction to enable secure holding of objects. In addition, a large contact area is preferably established between the fingers and the object. Enlargement of the contact area between a finger and the held object requires the finger (more specifically, area of the finger making contact with the object) to be given high flexibility so that it can deform in compliance with the shape or profile of the object.

However, when, as in the case of most conventional robot hands, the fingers are, in consideration of coefficient of friction, formed of a single rubber-based material of relatively high rigidity or stiffness such as silicone rubber, it is impossible to impart high enough flexibility to enable deformation in compliance with the shape of the object.

Moreover, in the prior art of Non-patent Ref. No. 1 and Patent Ref. No. 1, good flexibility cannot be achieved at the contact surface with a held object because a hard member (link) corresponding to a human bone is merely covered with a thin flexible member (comprising only one or two layers) corresponding to human skin.

A first object of this invention is therefore to overcome the aforesaid inconveniences by providing a robot hand that is improved in finger flexibility to enable objects to be grasped securely.

Another problem experienced is that when a force sensor is attached to a finger for detecting stress acting on the finger, the accuracy of stress detection decreases when the flexibility of the finger is increased.

A second object of this invention is therefore to provide a robot hand configured to improve finger flexibility, thereby enabling secure holding of objects, and improve the detection accuracy of a force sensor attached to the finger.

Means for Solving the Problems

BRIEF SUMMARY OF THE INVENTION

In accordance with an exemplary embodiment of the present invention there is provided a robot hand having a finger including finger links and finger joints interconnecting the links. At least one of the finger links includes a first member, a second member adhered to a surface of the first member, and a third member covering at least the second member. A rigidity of the second member is made smaller than the rigidities of the first member and the third member.

In accordance with certain exemplary embodiments, a coefficient of friction of the third member is made higher than the coefficients of friction of the first member and the second member.

In accordance with certain exemplary embodiments, a thickness of the third member is made smaller than the thickness of the second member.

In accordance with certain exemplary embodiments, the first member is made of a resin material.

In accordance with certain exemplary embodiments. the second member is made of a flexible material.

In accordance with certain exemplary embodiments, the third member is made of a material with a high coefficient of friction.

In accordance with certain exemplary embodiments, a surface of the third member is formed with a plurality of indentations.

In accordance with another exemplary embodiment of the present invention, the robot hand further includes: a fourth member adhered to a part of a surface of the third member; wherein the rigidity of the fourth member is made larger than the rigidity of the second member.

In accordance with certain exemplary embodiments, the fourth member is made of a resin material.

In accordance with another exemplary embodiment of the present invention there is provided a robot hand having a finger comprising finger links and finger joints interconnecting the links. At least one of the finger links includes a base to which a force sensor is attached, and a first member connected to the base through the force sensor. The finger link further includes a second member adhered to a surface of the first member, a third member covering at least the second member, and a fourth member adhered to a part of a surface of the third. The fourth member is interconnected with the force sensor.

In accordance with certain exemplary embodiments, the fourth member is interconnected with the force sensor through a connector.

BRIEF DESCRIPTION OF DRAWINGS

<figref idrefs="DRAWINGS">FIG. 1</figref> is a plan view of a robot hand seen from the palm side thereof according to a first embodiment of this invention;

<figref idrefs="DRAWINGS">FIG. 2</figref> is an explanatory diagram schematically illustrating the structure of a second finger shown in <figref idrefs="DRAWINGS">FIG. 1</figref>;

<figref idrefs="DRAWINGS">FIG. 3</figref> is a similar explanatory diagram schematically illustrating the structure of the second finger shown in <figref idrefs="DRAWINGS">FIG. 1</figref>;

<figref idrefs="DRAWINGS">FIG. 4</figref> is a perspective view, partially in section, of a distal link of the second finger shown in <figref idrefs="DRAWINGS">FIG. 1</figref>;

<figref idrefs="DRAWINGS">FIG. 5</figref> is a plan view of a first member shown in <figref idrefs="DRAWINGS">FIG. 4</figref>;

<figref idrefs="DRAWINGS">FIG. 6</figref> is a bottom view of the first member shown in <figref idrefs="DRAWINGS">FIG. 4</figref>;

<figref idrefs="DRAWINGS">FIG. 7</figref> is a sectional view taken along line VII-VII in <figref idrefs="DRAWINGS">FIG. 6</figref>;

<figref idrefs="DRAWINGS">FIG. 8</figref> is a plan view of a second member shown in <figref idrefs="DRAWINGS">FIG. 4</figref>;

<figref idrefs="DRAWINGS">FIG. 9</figref> is a bottom view of the second member shown in <figref idrefs="DRAWINGS">FIG. 4</figref>;

<figref idrefs="DRAWINGS">FIG. 10</figref> is a sectional view taken along line X-X in <figref idrefs="DRAWINGS">FIG. 9</figref>;

<figref idrefs="DRAWINGS">FIG. 11</figref> is a plan view of a third member shown in <figref idrefs="DRAWINGS">FIG. 4</figref>;

<figref idrefs="DRAWINGS">FIG. 12</figref> is a bottom view of the third member shown in <figref idrefs="DRAWINGS">FIG. 4</figref>;

<figref idrefs="DRAWINGS">FIG. 13</figref> is a sectional view taken along line XIII-XIII in <figref idrefs="DRAWINGS">FIG. 12</figref>;

<figref idrefs="DRAWINGS">FIG. 14</figref> is a perspective view showing the surface morphology of the third member shown in <figref idrefs="DRAWINGS">FIG. 4</figref>;

<figref idrefs="DRAWINGS">FIG. 15</figref> is a plan view of a fourth member <b>16</b><i>a</i><b>4</b> shown in <figref idrefs="DRAWINGS">FIG. 4</figref>;

<figref idrefs="DRAWINGS">FIG. 16</figref> is a bottom view of the fourth member <b>16</b><i>a</i><b>4</b> shown in <figref idrefs="DRAWINGS">FIG. 4</figref>;

<figref idrefs="DRAWINGS">FIG. 17</figref> is a sectional view taken along XVII-XVII in <figref idrefs="DRAWINGS">FIG. 15</figref>;

<figref idrefs="DRAWINGS">FIG. 18</figref> is a perspective view similar to <figref idrefs="DRAWINGS">FIG. 4</figref> showing a robot hand according to a second embodiment of the invention;

<figref idrefs="DRAWINGS">FIG. 19</figref> is a perspective view of a fourth member shown in <figref idrefs="DRAWINGS">FIG. 18</figref> etc.;

<figref idrefs="DRAWINGS">FIG. 20</figref> is a perspective view similar to <figref idrefs="DRAWINGS">FIG. 14</figref> showing the surface morphology of the third member shown in <figref idrefs="DRAWINGS">FIG. 4</figref> etc.; and

<figref idrefs="DRAWINGS">FIG. 21</figref> is a perspective view similarly showing the surface morphology of the third member shown in <figref idrefs="DRAWINGS">FIG. 4</figref> etc.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments for implementing the robot hand according to this invention are explained with reference to the attached drawing in the following.

First Embodiment

<figref idrefs="DRAWINGS">FIG. 1</figref> is a plan view seen from the palm side of a robot hand that is a first embodiment of this invention.

In <figref idrefs="DRAWINGS">FIG. 1</figref>, symbol <b>10</b> designates a robot hand. The robot hand <b>10</b> comprises a metacarpus (palm section) <b>12</b> and first to fifth fingers <b>14</b> to <b>22</b> connected to the palm <b>12</b>. The first to fifth fingers <b>14</b> to <b>22</b> correspond to the thumb, index finger, middle finger, ring finger and little finger of a human hand.

The metacarpus <b>12</b> comprises a palm forming member <b>30</b> that forms the surface of the palm of the hand and back forming member <b>32</b> that forms the surface of the back of the hand. First to fifth electric motors (stepping motors; not shown) for driving the five finger <b>14</b> to <b>22</b> are disposed inside the metacarpus <b>12</b>. The proximal end of the metacarpus <b>12</b> is connected to an arm <b>36</b> of a robot (not shown). The robot equipped with the arm <b>36</b> is a biped humanoid robot.

Each of the first to fifth fingers comprises a plurality of finger links and finger joints interconnecting the links. Specifically, the first finger (thumb) <b>14</b> comprises a distal link <b>14</b><i>a</i>, a proximal link <b>14</b><i>b</i>, first joint <b>14</b>A connecting the two links, and a second joint <b>14</b>B connecting the proximal link <b>14</b><i>b </i>and the metacarpus <b>12</b>. The second finger (index finger) <b>16</b> comprises a distal link <b>16</b><i>a</i>, a middle link <b>16</b><i>b</i>, a proximal link <b>16</b><i>c</i>, a first joint <b>16</b>A connecting the distal link <b>16</b><i>a </i>and middle link <b>16</b><i>b</i>, a second joint <b>16</b>B connecting the middle link <b>16</b><i>b </i>and proximal link <b>16</b><i>c</i>, and a third joint <b>16</b>C connecting the proximal link <b>16</b><i>c </i>and the metacarpus <b>12</b>. The third finger <b>18</b>, fourth finger <b>20</b> and fifth finger <b>22</b> are structured similarly to the second finger <b>16</b>.

<figref idrefs="DRAWINGS">FIGS. 2 and 3</figref> are explanatory diagrams schematically illustrating the structure of the second finger <b>16</b>.

As illustrated, the proximal link <b>16</b><i>c </i>is connected through the third joint <b>16</b>C to a fixed member <b>38</b> fastened to the metacarpus <b>12</b>. The second finger <b>16</b> is further equipped with a first arm <b>161</b> extending parallel to the middle link <b>16</b><i>b </i>and a second arm <b>162</b> extending parallel to the proximal link <b>16</b><i>c. </i>

One end of the first arm <b>161</b> is connected to the proximal link <b>16</b><i>c </i>at a point near a second joint pivot shaft <b>16</b>BS and the other end thereof is connected to the distal link <b>16</b><i>a </i>at a point near a first joint pivot shaft <b>16</b>AS. One end of the second arm <b>162</b> is connected to the fixed member <b>38</b> fastened to the metacarpus <b>12</b> and the other end thereof is connected to the middle link <b>16</b><i>b </i>at a point near the second joint pivot shaft <b>16</b>BS.

The third joint <b>16</b>C is connected to the output shaft of an electric motor not shown in the drawings. When the third joint <b>16</b>C (proximal link <b>16</b><i>c</i>) is rotated by the rotational output of the electric motor, the second joint <b>16</b>B (middle link <b>16</b><i>b</i>) is rotated via the second arm <b>162</b>, and the first joint <b>16</b>A (distal link <b>16</b><i>a</i>) is rotated through the first arm <b>161</b>. As a result, the second finger <b>16</b> is bent as shown in <figref idrefs="DRAWINGS">FIG. 3</figref>.

Like the second finger <b>16</b>, the third finger <b>18</b>, fourth finger <b>20</b> and fifth finger <b>22</b> are also provided with first arms and second arms (not shown) and are driven by electric motors (not shown) connected to their third joints to perform bending movement. The first finger <b>14</b> is equipped with only a first arm (not shown) extending parallel to the proximal link <b>14</b><i>b </i>and is driven by an electric motor (not shown) connected to the second joint to perform bending movement.

As set out in the foregoing, in the robot hand <b>10</b> according to this embodiment, the fingers can be bent to grasp an object by operating the electric motors connected to the third joints (or second joint) of the fingers.

The fingertip structure of the fingers that is the characterizing feature of this invention will now be explained with reference to <figref idrefs="DRAWINGS">FIGS. 4 to 17</figref>.

<figref idrefs="DRAWINGS">FIG. 4</figref> is a perspective view, partially in section, of the distal link <b>16</b><i>a </i>of the second finger <b>16</b>.

The fingertip structure of the robot hand according to this embodiment will be explained taking the distal link <b>16</b><i>a </i>as an example. As illustrated, the distal link <b>16</b><i>a </i>is provided with a first member <b>16</b><i>a</i><b>1</b> situated in the middle of the distal link <b>16</b><i>a</i>, a second member <b>16</b><i>a</i><b>2</b> adhered to part of the surface of the first member <b>16</b><i>a</i><b>1</b>, a third member <b>16</b><i>a</i><b>3</b> covering the first member <b>16</b><i>a</i><b>1</b> and second member <b>16</b><i>a</i><b>2</b>, and a fourth member <b>16</b><i>a</i><b>4</b> adhered to part of the surface of the third member. The first member <b>16</b><i>a</i><b>1</b> to fourth member <b>16</b><i>a</i><b>4</b> correspond to the bone, flesh, skin and nail of a human fingertip.

The first member <b>16</b><i>a</i><b>1</b> is connected to a base <b>42</b> through a force sensor (three-axis force sensor) <b>40</b> and a high-rigidity cylindrical member <b>40</b><i>a </i>made of metal or a resin material that is fastened to the force sensor <b>40</b>. The base <b>42</b> is connected to the middle link <b>16</b><i>b </i>through the first joint <b>16</b>A.

<figref idrefs="DRAWINGS">FIG. 5</figref> is a plan view of the first member <b>16</b><i>a</i><b>1</b> (seen from the side of the fourth member <b>16</b><i>a</i><b>4</b>). <figref idrefs="DRAWINGS">FIG. 6</figref> is a bottom view of the first member <b>16</b><i>a</i><b>1</b> (seen from below in the drawing sheet of <figref idrefs="DRAWINGS">FIG. 5</figref>). <figref idrefs="DRAWINGS">FIG. 7</figref> is a sectional view taken along line VII-VII in <figref idrefs="DRAWINGS">FIG. 6</figref>.

As shown in <figref idrefs="DRAWINGS">FIGS. 5 to 7</figref>, the first member <b>16</b><i>a</i><b>1</b> is provided with a first hole <b>16</b><i>a</i><b>11</b>, a second hole <b>16</b><i>a</i><b>12</b>, and a third hole <b>16</b><i>a</i><b>13</b> lying orthogonal to the second hole <b>16</b><i>a</i><b>12</b>. In the first member <b>16</b><i>a</i><b>1</b>, the surface designated by the symbol <b>16</b><i>a</i><b>14</b> (indicated by bold lines in <figref idrefs="DRAWINGS">FIGS. 6 and 7</figref>) is a surface contacted by the second member <b>16</b><i>a</i><b>2</b> (hereinafter called the “second member contact surface”). The second member contact surface <b>16</b><i>a</i><b>14</b> is given an inclination of a prescribed angle α (e.g., about 40 degrees) relative to the longitudinal direction of the distal link <b>16</b><i>a</i>. The first member <b>16</b><i>a</i><b>1</b> is made of a resin material (in this embodiment, epoxy resin material).

<figref idrefs="DRAWINGS">FIG. 8</figref> is a plan view of the second member <b>16</b><i>a</i><b>2</b>. <figref idrefs="DRAWINGS">FIG. 9</figref> is a bottom view of the second member <b>16</b><i>a</i><b>2</b> (seen from below in the drawing sheet of <figref idrefs="DRAWINGS">FIG. 8</figref>). <figref idrefs="DRAWINGS">FIG. 10</figref> is a sectional view taken along line X-X in <figref idrefs="DRAWINGS">FIG. 9</figref>. In <figref idrefs="DRAWINGS">FIGS. 9 and 10</figref>, the surface designated by symbol <b>16</b><i>a</i><b>21</b> (indicated by bold lines) is a surface contacted by the second member contact surface <b>16</b><i>a</i><b>14</b> (hereinafter called the “first member contact surface”). The first member contact surface <b>16</b><i>a</i><b>21</b> is shaped to run along the second member contact surface <b>16</b><i>a</i><b>14</b>. The second member <b>16</b><i>a</i><b>2</b> is made of a flexible material having flexibility of an HS hardness of around 2 to 15 (in this embodiment, gel elastomer) and is fastened to the first member <b>16</b><i>a</i><b>1</b> through an elastic adhesive or the like.

<figref idrefs="DRAWINGS">FIG. 11</figref> is a plan view of the third member <b>16</b><i>a</i><b>3</b>. <figref idrefs="DRAWINGS">FIG. 12</figref> is a bottom view of the third member <b>16</b><i>a</i><b>3</b> (seen from below in the drawing sheet of <figref idrefs="DRAWINGS">FIG. 11</figref>). <figref idrefs="DRAWINGS">FIG. 13</figref> is a sectional view taken along line XIII-XIII in <figref idrefs="DRAWINGS">FIG. 12</figref>. <figref idrefs="DRAWINGS">FIG. 14</figref> is a perspective view showing the surface morphology of the third member <b>16</b><i>a</i><b>3</b>. As shown in <figref idrefs="DRAWINGS">FIGS. 11 to 13</figref>, the third member <b>16</b><i>a</i><b>3</b> is pouch-like.

The third member <b>16</b><i>a</i><b>3</b> is formed with a first hole <b>16</b><i>a</i><b>31</b>, second hole <b>16</b><i>a</i><b>32</b> and a third hole <b>16</b><i>a</i><b>33</b>. In the third member <b>16</b><i>a</i><b>3</b>, the surface designated by the symbol <b>16</b><i>a</i><b>34</b> (indicated by bold lines in <figref idrefs="DRAWINGS">FIGS. 12 and 13</figref>) is a surface contacted by the fourth member <b>16</b><i>a</i><b>4</b> (hereinafter called the “fourth member contact surface”). The third member <b>16</b><i>a</i><b>3</b> is made of a material with a high coefficient of friction (in this embodiment, urethane material), and its surface is formed with a plurality of indentations <b>16</b><i>a</i><b>35</b> that give it a bumpy (dimpled) shape, as shown in <figref idrefs="DRAWINGS">FIG. 14</figref>, and is imparted with a high coefficient of friction (more exactly, coefficient of static friction) of around 1 to 10.

<figref idrefs="DRAWINGS">FIG. 15</figref> is a plan view of the fourth member <b>16</b><i>a</i><b>4</b>. <figref idrefs="DRAWINGS">FIG. 16</figref> is a bottom view of the fourth member <b>16</b><i>a</i><b>4</b> (seen from below in the drawing sheet of <figref idrefs="DRAWINGS">FIG. 15</figref>). <figref idrefs="DRAWINGS">FIG. 17</figref> is a sectional view taken along XVII-XVII in <figref idrefs="DRAWINGS">FIG. 16</figref>. As shown in <figref idrefs="DRAWINGS">FIGS. 15 to 17</figref>, the fourth member <b>16</b><i>a</i><b>4</b> is formed with a fourth hole <b>16</b><i>a</i><b>41</b> and a projection <b>16</b><i>a</i><b>42</b>. In the fourth member <b>16</b><i>a</i><b>4</b>, the surface designated by the symbol <b>16</b><i>a</i><b>43</b> (indicated by bold lines in <figref idrefs="DRAWINGS">FIGS. 16 and 17</figref>) is a surface contacted by the fourth member contact surface <b>16</b><i>a</i><b>34</b> (hereinafter called the “third member contact surface”). Like the first member <b>16</b><i>a</i><b>1</b>, the fourth member <b>16</b><i>a</i><b>4</b> is made of a resin material (in this embodiment, epoxy resin material).

<figref idrefs="DRAWINGS">FIG. 4</figref> will now be explained again against the backdrop of the foregoing description. The second member <b>16</b><i>a</i><b>2</b> (more exactly, the first member contact surface <b>16</b><i>a</i><b>21</b> thereof) is adhered to part of the surface of the first member <b>16</b><i>a</i><b>1</b> (the second member contact surface <b>16</b><i>a</i><b>14</b>). The first member <b>16</b><i>a</i><b>1</b> and the second member <b>16</b><i>a</i><b>2</b> adhered thereto are inserted into the pouch-like third member <b>16</b><i>a</i><b>3</b> through the third hole <b>16</b><i>a</i><b>33</b> to be covered by third member <b>16</b><i>a</i><b>3</b>. The thickness of the third member <b>16</b><i>a</i><b>3</b> is made thinner than that of the second member <b>16</b><i>a</i><b>2</b>. Specifically, the third member <b>16</b><i>a</i><b>3</b> is given a thickness at portions that contact the second member <b>16</b><i>a</i><b>2</b> that is about one-sixth that of the second member <b>16</b><i>a</i><b>2</b>.

The rigidity of the second member <b>16</b><i>a</i><b>2</b> is made smaller than that of the third member <b>16</b><i>a</i><b>3</b>. As mentioned earlier, the second member <b>16</b><i>a</i><b>2</b> in this embodiment is fabricated of gel elastomer material and the third member <b>16</b><i>a</i><b>3</b> is fabricated of urethane material, so that the rigidity or stiffness of the second member <b>16</b><i>a</i><b>2</b> is made smaller than that of the third member <b>16</b><i>a</i><b>3</b>.

The fourth member <b>16</b><i>a</i><b>4</b> (more exactly, the third member contact surface <b>16</b><i>a</i><b>43</b> thereof) is adhered to part of the surface of the third member <b>16</b><i>a</i><b>3</b> (the fourth member contact surface <b>16</b><i>a</i><b>34</b>). At this time, the projection <b>16</b><i>a</i><b>42</b> formed on the fourth member <b>16</b><i>a</i><b>4</b> is inserted into the first hole <b>16</b><i>a</i><b>31</b> formed in the third member <b>16</b><i>a</i><b>3</b> and the first hole <b>16</b><i>a</i><b>11</b> formed in the first member <b>16</b><i>a</i><b>1</b>, whereby the first member <b>16</b><i>a</i><b>1</b>, third member <b>16</b><i>a</i><b>3</b> and fourth member <b>16</b><i>a</i><b>4</b> are positioned at prescribed locations. As is clear from the foregoing explanation, the surface region of the third member <b>16</b><i>a</i><b>3</b> other than that to which the fourth member <b>16</b><i>a</i><b>4</b> is adhered (the fourth member contact surface <b>16</b><i>a</i><b>34</b>) constitutes a contact surface when an object is grasped.

Generally, a higher coefficient of friction can be obtained with the urethane material forming the third member <b>16</b><i>a</i><b>3</b> than with the gel elastomer material forming the second member <b>16</b><i>a</i><b>2</b> or the epoxy resin material forming the first member <b>16</b><i>a</i><b>1</b>. Moreover, the coefficient of friction of the finger is further enhanced by making the surface of the third member <b>16</b><i>a</i><b>3</b> bumpy (dimpled), so that when the robot hand <b>10</b> grasps an object it can hold it securely.

Owing to the fabrication of the second member <b>16</b><i>a</i><b>2</b> of a gel elastomer material that is lower in rigidity and higher in flexibility than the third member <b>16</b><i>a</i><b>3</b>, the second member <b>16</b><i>a</i><b>2</b> and the third member <b>16</b><i>a</i><b>3</b> that covers it can readily deform in compliance with the shape or profile of a held object. That is, the finger is imparted with high flexibility so as to increase the contact area between the finger (third member <b>16</b><i>a</i><b>3</b>) and the held object, thereby making it possible to hold the object securely. Moreover, owing to the fact that the gel elastomer material forming the second member <b>16</b><i>a</i><b>2</b> exhibits not only high flexibility but also restoring force, the finger can be restored to its original shape when the contact between the finger and the held object is terminated.

In addition, the thickness of the third member <b>16</b><i>a</i><b>3</b> is made smaller than the thickness of the second member <b>16</b><i>a</i><b>2</b>, so that deformation of the second member <b>16</b><i>a</i><b>2</b> is promoted to enhance the flexibility of the finger still further.

Owing to the fact that the first member <b>16</b><i>a</i><b>1</b> is made of epoxy resin, i.e., since the first member <b>16</b><i>a</i><b>1</b> is fabricated of a material that exhibits high rigidity and is also light in weight, the inertia mass of the finger is reduced to reduce the electric motor load, thereby making it possible to reduce the size and weight of the motor. Further, stress acting on the finger can be detected with good accuracy because the force sensor <b>40</b> is attached to the first member <b>16</b><i>a</i><b>1</b> exhibiting high rigidity.

Furthermore, the attachment of the fourth member <b>16</b><i>a</i><b>4</b> of higher rigidity than the second member <b>16</b><i>a</i><b>2</b> enables the fourth member <b>16</b><i>a</i><b>4</b> to inhibit excessive deformation of the highly flexible second member <b>16</b><i>a</i><b>2</b>, so that objects can be held still more securely. Moreover, the fourth member <b>16</b><i>a</i><b>4</b> is fabricated of epoxy resin so as to be low in weight, thereby helping to minimize the inertia mass of the finger.

The explanation of <figref idrefs="DRAWINGS">FIG. 4</figref> will be resumed. The cylindrical member <b>40</b><i>a </i>is fastened in the third hole <b>16</b><i>a</i><b>13</b> formed in the first member <b>16</b><i>a</i><b>1</b>. The cylindrical member <b>40</b><i>a </i>is formed with a hole and a high-rigidity pin (connector) <b>44</b> made of a metal or resin material is inserted through this hole, the second hole <b>16</b><i>a</i><b>12</b> formed in the first member <b>16</b><i>a</i><b>1</b>, the second hole <b>16</b><i>a</i><b>32</b> formed in the third member <b>16</b><i>a</i><b>3</b>, and the fourth hole <b>16</b><i>a</i><b>41</b> formed in the fourth member <b>16</b><i>a</i><b>4</b>, thereby interconnecting the fourth member <b>16</b><i>a</i><b>4</b> and the force sensor <b>40</b>.

Owing to the interconnection of the force sensor <b>40</b> and the fourth member <b>16</b><i>a</i><b>4</b> that is located at the outermost of the finger link and exhibits high rigidity, stress received by the finger is accurately transmitted to the force sensor <b>40</b> through the fourth member <b>16</b><i>a</i><b>4</b>, thereby enhancing the detection accuracy of the force sensor <b>40</b>.

The interconnection of the fourth member <b>16</b><i>a</i><b>4</b> with the force sensor <b>40</b> through the cylindrical member <b>40</b><i>a </i>and the pin <b>44</b> simplifies the shape of the fourth member <b>16</b><i>a</i><b>4</b>. This makes it easy to fabricate the fourth member <b>16</b><i>a</i><b>4</b> and also facilitates its connection (assembly) with the force sensor <b>40</b>.

In the forgoing, the configuration of a finger link was explained taking the distal link <b>16</b><i>a </i>of the second finger <b>16</b> as an example. This configuration is also suitable for the distal links of the other fingers, notwithstanding some differences in the shapes and dimensions of particular portions. The structural features explained in the foregoing, aside from the base, force sensor and the fourth member corresponding to a nail, apply similarly to middle links and proximal links of the individual fingers, i.e., each is structured of first, second and third members that resemble the foregoing in arrangement order and materials. Explanation thereof will therefore be omitted. The metacarpus <b>12</b> to which the fingers are connected is also structured of first, second and third members whose arrangement order and materials are similar to the foregoing. Explanation thereof will therefore be omitted.

Thus in this embodiment, the robot hand <b>10</b> is given a high coefficient of friction and high flexibility overall, thereby further enhancing holding performance. Further, the formation of the first member corresponding to a bone of light-weight epoxy resin material reduces the inertia mass of the robot hand <b>10</b> attached to the end of the robot arm <b>36</b>.

Second Embodiment

A second embodiment of this invention will now be explained with reference to <figref idrefs="DRAWINGS">FIGS. 18 and 19</figref>. <figref idrefs="DRAWINGS">FIG. 18</figref> is a perspective view similar to <figref idrefs="DRAWINGS">FIG. 4</figref> showing a robot hand according to the second embodiment of the invention.

Explanation will be made with focus on points of difference from the first embodiment. In the second embodiment, the fourth member <b>16</b><i>a</i><b>4</b> is provided with a connector <b>16</b><i>a</i><b>45</b> that serves in place of the pin interconnecting the fourth member <b>16</b><i>a</i><b>4</b> and cylindrical member <b>40</b><i>a. </i>

<figref idrefs="DRAWINGS">FIG. 19</figref> is a perspective view of the fourth member <b>16</b><i>a</i><b>4</b> in the second embodiment. As illustrated, the connector <b>16</b><i>a</i><b>45</b> provided on the fourth member <b>16</b><i>a</i><b>4</b> is formed with an insertion hole <b>16</b><i>a</i><b>46</b>. As shown in <figref idrefs="DRAWINGS">FIG. 18</figref>, the cylindrical member <b>40</b><i>a </i>to which the force sensor <b>40</b> is attached is inserted into the insertion hole <b>16</b><i>a</i><b>46</b>, thereby interconnecting the fourth member <b>16</b><i>a</i><b>4</b> and the force sensor <b>40</b>.

As a result, similarly to in the first embodiment, stress received by the finger is accurately transmitted to the force sensor <b>40</b> through the fourth member <b>16</b><i>a</i><b>4</b>, thereby enhancing the detection accuracy of the force sensor <b>40</b>.

The remaining structural features of the second embodiment are the same as those of the first embodiment and will not be explained again.

As mentioned above, the first and second embodiments of this invention is configured to have a robot hand (<b>10</b>) having a finger (first to fifth finger <b>14</b> to <b>22</b>) comprising finger links (distal links <b>14</b><i>a </i>to <b>22</b><i>a</i>, middle links <b>16</b><i>b </i>to <b>22</b><i>b</i>, proximal links <b>14</b><i>b</i>, <b>16</b><i>c </i>to <b>22</b><i>c</i>) and finger joints (first joints <b>14</b>A to <b>22</b>A, second joints <b>14</b>B to <b>22</b>B, third joints <b>16</b>C to <b>22</b>C) interconnecting the links, characterized in that: at least one of the finger links comprises; a first member (<b>16</b><i>a</i><b>1</b>); a second member (<b>16</b><i>a</i><b>2</b>) adhered to a surface of the first member; and a third member (<b>16</b><i>a</i><b>3</b>) covering at least the second member; and that a rigidity of the second member (<b>16</b><i>a</i><b>2</b>) is made smaller than the rigidities of the first member (<b>16</b><i>a</i><b>1</b>) and the third member (<b>16</b><i>a</i><b>3</b>).

It is configured such that a coefficient of friction of the third member (<b>16</b><i>a</i><b>3</b>) is made higher than the coefficients of friction of the first member (<b>16</b><i>a</i><b>1</b>) and the second member (<b>16</b><i>a</i><b>2</b>).

It is configured such that a thickness of the third member (<b>16</b><i>a</i><b>3</b>) is made smaller than the thickness of the second member (<b>16</b><i>a</i><b>2</b>).

It is configured such that the first member (<b>16</b><i>a</i><b>1</b>) is made of a resin material.

It is configured such that the second member (<b>16</b><i>a</i><b>2</b>) is made of a flexible material.

It is configured such that the third member (<b>16</b><i>a</i><b>3</b>) is made of a material with a high coefficient of friction.

It is configured such that a surface of the third member (<b>16</b><i>a</i><b>3</b>) is formed with a plurality of indentations.

It is configured to further include: a fourth member (<b>16</b><i>a</i><b>4</b>) adhered to a part of a surface of the third member (<b>16</b><i>a</i><b>3</b>); wherein the rigidity of the fourth member (<b>16</b><i>a</i><b>4</b>) is made larger than the rigidity of the second member (<b>16</b><i>a</i><b>2</b>).

It is configured such that the fourth member (<b>16</b><i>a</i><b>4</b>) is made of a resin material.

It is configured to have a robot hand (<b>10</b>) having a finger (first to fifth finger <b>14</b> to <b>22</b>) comprising finger links (distal links <b>14</b><i>a </i>to <b>22</b><i>a</i>, middle links <b>16</b><i>b </i>to <b>22</b><i>b</i>, proximal links <b>14</b><i>b</i>, <b>16</b><i>c </i>to <b>22</b><i>c</i>) and finger joints (first joints <b>14</b>A to <b>22</b>B, second joints <b>14</b>B to <b>22</b>B, third joints <b>16</b>C to <b>22</b>C) interconnecting the links, characterized in that: at least one of the finger links comprises; a base (<b>42</b>) to which a force sensor (<b>40</b>) is attached; a first member (<b>16</b><i>a</i><b>1</b>) connected to the base (<b>42</b>) through the force sensor (<b>40</b>); a second member (<b>16</b><i>a</i><b>2</b>) adhered to a surface of the first member (<b>16</b><i>a</i><b>1</b>); a third member (<b>16</b><i>a</i><b>3</b>) covering at least the second member (<b>16</b><i>a</i><b>2</b>); and a fourth member (<b>16</b><i>a</i><b>4</b>) adhered to a part of a surface of the third member (<b>16</b><i>a</i><b>3</b>); and that the fourth member (<b>16</b><i>a</i><b>4</b>) is interconnected with the force sensor (<b>40</b>).

In the first embodiment, it is configured such that the fourth member (<b>16</b><i>a</i><b>4</b>) is interconnected with the force sensor (<b>40</b>) through a connector (cylindrical member <b>40</b><i>a</i>, pin <b>44</b>).

Although it is explained in the foregoing that the first member <b>16</b><i>a</i><b>1</b> and fourth member <b>16</b><i>a</i><b>4</b> are fabricated of epoxy resin, they can instead be made of ABS, PEEK or other resin material. Although it is explained that the second member <b>16</b><i>a</i><b>2</b> is fabricated of gel elastomer material, it can instead be made of sponge or other such flexible material. Although it is explained that the third member <b>16</b><i>a</i><b>3</b> is fabricated of urethane, it can instead be made of silicone rubber or other such material having a high coefficient of friction. In other words, the materials of the individual components are not limited to those set out as examples but can be suitably selected in accordance with the kind of objects the robot hand is intended to hold.

Although it is explained that all of the finger links (distal link, middle link and proximal link) and the metacarpus are structured of first to third members, it is possible to provide only some of the finger links and the metacarpus with first to third materials.

Although the surface morphology of the third member <b>16</b><i>a</i><b>3</b> is explained as being dimpled, it is only required to be irregular and any of various other morphologies can be adopted, including, for example, the striped pattern of <figref idrefs="DRAWINGS">FIG. 20</figref> formed of numerous evenly spaced linear grooves <b>16</b><i>a</i><b>36</b> or the human fingerprint pattern of <figref idrefs="DRAWINGS">FIG. 21</figref> formed of numerous curved grooves <b>16</b><i>a</i><b>37</b>.

INDUSTRIAL APPLICABILITY

In accordance with this invention, at least one finger link of a robot hand comprises a first member, a second member adhered to the surface of the first member, and a third member covering at least the second member, and the rigidity of the second member is made lower than the rigidity of the first member and the third member. As a result, the flexibility of the finger is improved by the second member, thereby increasing the contact area between the third member and a held object, so that the object can be securely held.